Play balls

ABSTRACT

Playballs, particularly golf balls, which are moulded from a composition which includes a blend of rubber with a thermoplastic homopolymer or copolymer of an alpha-olefine. The balls may be single-piece mouldings or mouldings of a one, two or more piece core encased in a cover.

United States Patent Stanley R. Harrison Castle Bromwich, nearBirmingham; Robert M. Broughton, Boldmere, Sutton Coldfield, EnglandJune 29, 1967 Mar. 30, 1971 The Dunlop Company Limited London County,England July 22, 1966, Mar. 7, 1967 Great Britain 32,952/66 and 10734/67lnventors Appl. No. Filed Patented Assignee Priority PLAY BALLS 16Claims, No Drawings [56] ReferencesCited UNITED STATES PATENTS 3,421,7661/1969 Chimiel e161 260/889 2,910,451 10/1959 Cantwell.. 260/8892,914,328 11/1959 Harkins.... 273/230 3,313,545 4/1967 Bartsch....'273/218 3,373,123 3/1968 Brice 260/2.5

1 011131019 PATENTS 217,159 5/1957 Australia 260/889 1,026,254 4/1966GreatBritain 273/330 Primary Examiner-John C. Bleutge AttorneyStevens,Davis, Miller and Mosher ABSTRACT: Playballs, particularly golf balls,which are moulded from a composition which includes a blend of rubberwith a thermoplastic homopolymer or copolymer of an alphaolefine. Theballs may be single-piece mouldings or mouldings of a one, two or morepiece core encased in a cover.

PLAY BALLS This invention relates to playballs and particularly toplayballs for use as golf balls for general playing purposes and forpractice on driving ranges.

Golf balls for use in tournaments and competitions are of a high qualitywith regard to durability, flight and playing characteristics, but suchgolf balls are expensive. For general playing purposes and for practice,such as on a driving range, it is usual to use a cheaper ball than thetournament balls, but the cheaper balls is required to have durability,flight characteristics and playing characteristics which do not differgreatly from those of a tournament ball. In particular, the practiceball is required to have good resistance to cutting and good flightcharacteristics such that when struck with a golf club the ball willtravel approximately the same distance as a tourname'nt ball wouldtravel. Also, the practice ball should preferably have the same feelwhen struck as a tournament ball and should preferably result in thesame click" when struck as is given by a tournament ball.

According to the present invention there is provided a play lar weightcis-polybutadiene is preferred, cg. a polymer having a molecular weightof from 2x10 to 2X10.

The blend of the thermoplastic homopolymer or copolymcr and the rubbercan be prepared by mixing the two components together on a mill or in aninternal mixer at an elevated temperature. The temperature canconveniently be from 30 C. to 50 C. higher than the melting point of thethermoplastic component. Fillers, coloring agents and antioxidants, ifrequired, can be added to the blend during this mixing. The blend is thecooled to 1 C. to 125 C. prior to the addition of curing agents ifdesired, after which the composition can be cooled and chipped orgranulated.

ball comprising a blend of rubber and a thermoplastic, sub- I stantiallycrystalline homopolymer or copolymer. of an alphaolefme, the rubberbeing present in the blend in an amount of from 5 percent to 95 percentby weight of the blend.

For example, suitable blends include blends of rubber and athermoplastic, substantially crystalline homopolymer of ethylene or acopolymer obtained by copolymerizing a major amount of ethylene with aminor amount of another olefme, the rubber being present in the blend inan amount of 5 percent to 95 percent by weight of the blend. Othersuitable blends include those of rubber and a thermoplastic,substantially crystalline homopolymer of propylene or copolymer obtainedby copolymerizing a major amount of propylene with a minor amount ofanother olefine, the rubber being present in the blend in an amount of 5percent by 95 percent by weight of the blend.

Preferably, the alpha-olefine homopolymer contains not more than sixcarbon atoms and may be ethylene, isotactie polypropylene, isotacticpolybutene-l or isotactic poly-4- methyl-pentenel The copolymerizableolefine preferably contains not more than eight carbon atoms and may bebutene-l hexene-l, ethylene or propylene, where these materials are notthe primary olefme in the copolymer.

Said copolymer can be a terpolymer containing preferably not more than10 percent, and especially not more than 5 percent of other unsaturatedmonomers. A preferred third monomer is butadiene.

Blends of various homopolymers and/or copolymers may be used.

According to the present invention there is also provided a method forthe manufacture of a ball suitable for use as a golf ball, comprisingforming a composition including a blend of rubber and a thermoplastic,substantially crystalline homopolymer or copolymer of an alpha-olefine,the rubber being present in the blend in an amount of from 5 percent to95 percent by weight of the blend, adding filler if desired to saidcomposition and moulding the blend obtained to form a ball.

The amount of rubber is usually from 50 to 90 percent by weight andpreferably from 60 to 80 percent by weight.

The rubber used may be natural or synthetic and examples of suitablesynthetic rubbers are polybutadiene, (especially cis-polybutadiene),copolymers of butadiene with styrene or acrylonitrile, polybutylene,copolymers (elastomeric) of ethylene with propylene or higheralpha-olefmes, polyisoprene and polychloroprene. It is to be understoodthat blends or mixtures of synthetic rubbers, or of natural rubber andone or more synthetic rubbers, may be used. Preferably, the rubber iscispolybutadiene or a blend or mixture of cispolybutadiene with naturalrubber, and in this latter case the cis-polybutadiene should be presentin an amount of at least 50 percent by weight of the blend of mixture. Ahigh molecu- The composition is preferably cured and this is preferablyeffected by the use of organic peroxide curing agents such as dicumylperoxide, or if desired, curing can be effected by irradiation or bysulfur. Usually, sulfur only results in the crosslinking of only therubber component and so it is preferred to use a peroxide curing agentwhich results in cross-linking of both or all of the components of theblend to yield a highly resilient ball which is not deformed under theconditions of impact by a golf club. In the case of crystallinecopolymers containing unsaturation, sulfur will result in cross-linkingof both or all of the components of the blend.

Usually, the curable composition of the blend will be cured by heatingit in the presence of a curing agent at an elevated temperature andsuitable temperatures are from 150 C. to 250 C. The composition is alsomoulded to form the ball at a temperature usually from 150 C. to 350 C.and so moulding and curing are usually effected substantiallysimultaneously. The composition can be formed into the ball by a varietyof moulding techniques, e.g. injection, compression or transfermoulding. When the composition is cured by heating, the time requiredfor curing will usually be short, say 20 to 60 minutes, depending uponthe half-life of the peroxide curing agent used.

The amount of filler material is usually from 30 to 70 percent by weightof the polymer and depends on the size and weight of the ball to beproduced. Whilst most fillers can be used those with a very highspecific gravity are preferred in order to reduce the required loadingto a minimum.

A ball of the present invention can be a one-piece moulded ball or acomposite ball consisting of two or more portions, for example the ballcan comprise a core and cover, the core comprising a blend of rubber anda thermoplastic, substantially crystalline homopolymer or copolymer ofan alpha-olefine, the rubber being present in the blend in an amount offrom 5 percent to 95 percent by weight of the blend.

The cover can be of the same composition as the core or different. Forexample, the cover can be of one or more of the following: a blend ofthe types disclosed in our British Pat. applications Nos. 32,953/66 and32,954/66, balata; transpolymers of a conjugated diolefine, for instancetranspolyisoprene, trans-polybutadiene, (preferably having atranspolymer content of at least percent); cis-polymers of conju gateddiolefines; for instance cispolyisoprene, cis-polybutadiene, preferablyhaving a cis-polymer content of at least 50 percent; natural rubber;polyurethanes; polyamides; copolymers of butadiene and styrene; polymersand copolymers of ethylene; polymers and copolymers of propylene;compositions of our British Pat. applications Nos. 5,693/65 and38,674/65 or copolymers of unsaturated olefmes with esters ofunsaturated acids, for instance methyl methacrylate-butadienecopolymers, especially those of high (especially predominating) methylmethacrylate content; neoprene, especially in crystalline form.

The cover can be one or more of the elastomeric materials disclosed inBritish Specification No. 1,037,091.

The cover composition can contain a filler, for example inorganicfillers such as silica lead carbonate or titanium dioxide, the latterbeing especially useful in providing a white appearance to the ball.

The term copolymer used in this Specification includes polymers obtainedfrom two, three or more reactants (which can be monomers or partiallypolymerized materials), interpolymers, block polymers, and blendsthereof.

The method by which the cover is fixed to the core depends upon thenature of the material used for the cover. Where it is a thermoplasticmaterial it can be applied either by an injection moulding process, forinstance one in which molten material is forced around the periphery ofthe core centrally mounted in a spherical mould, or it can be appliedfor instance in the form of two hemispherical shells encasing the coreand which are moulded to the core and are sealed together along theiredges to form a smooth integral spherical shell cover. The latterprocess can also be used where the material used for the cover is notthermoplastic.

The means by which the cover is fixed to the core depends very much uponthe nature of the cover and core. Where the cover is formed by a processof injection moulding around the core there is normally no need forauxiliary means of fixing as the material of the cover will, while stillmolten, flow into intimate contact with the periphery of the coreresulting in a strong bond between the two portions of the ball.However, where the cover is moulded, for example by compression mouldingfrom two hemispherical shells it may be necessary to use auxiliary meansof fixing, for example an adhesive. An alternative auxiliary means offixing is by mechanical interlocking means, for example by fonning thecore so as to have protruberances or recesses in its surface on to whichthe cover can lock when moulded onto the core.

A further form of golf ball according to the present invention is one inwhich the core itself consists of two or more portions. Such a structureis very useful where it is wished to concentrate the weight of the ballon the center, through it can be used in other circumstances. In such astructure the core can consist of a spherical inner portion or innercore (for instance a glass or steel ball) surrounded by two or moreouter core portions which together form a spherical shell about it. Forexample, if there are two outer core portions they can be in the form ofhollow hemispherical shells which together surround the inner core toform a composite structure of spherical shape. The material composingthe inner core and outer core portions can be the same or different, andone or more of the inner core or outer core portions can comprise theblend of natural or synthetic rubber with a thermoplastic olefine,homopolymer or copolymer as described above.

The dimensions of the components of a composite golf ball according tothe present invention may suitably be as follows:

As for two component ball Cover thickness The present invention providesa ball which can be produced more economically than a conventional golfball. Golf balls for use in tournament and competitions usually consistessentially of a core comprising a core center of paste contained in aspherical rubber sac wound with rubber thread and/or rubber tape, and acover compound of balata or the like moulded on to the core. Such ballshave excellent durability, flight and playing characteristics but theyare expensive to produce due to the lengthy procedure of manufacture. Acheaper ball is required for general playing purposes and for practice(e.g. on practice driving ranges) and hitherto such balls, in commercialuse, have usually had essentially the same construction as thetournament ball but having a solid rubber center and having a cover madeof a cheaper material (eg polychloroprene) than the tournament ball.These practice balls are durable but they are nevertheless stillrelatively expensive to produce.

The present invention provides a ball moulded from a polymer compositionwithout a thread-wound core, which has good flight characteristics.

The balls of the present invention, especially where they are one-piecemoulded balls of uniform density throughout, can

with advantage have a surface pattern according to our EXAMPLE 1.

Twenty-seven and five tenths parts of a terpolymer of ethylene with aminor amount of butene-l and less than 5 percent by weight of butadienewere mixed with 72.5 parts of cispolybutadiene (cis-content 97 percent,ML-4 at 100 C. of 50) in an internal mixer at a temperature of C. to C.until a homogeneous blend resulted. Forty-eight parts of lead carbonate,three parts of titanium dioxide and one part of yellow pigment (foridentification) were then added and mixing continued until a homogeneousblend again resulted. The mix was cooled to l20 C. and 3.25 parts ofdicumyl peroxide were added.

The blend was then sheeted on a mill and the composition rapidly cooledto room temperature. The resulting sheet had a thickness of 0. l 20inch.

Slabs 3 inches by 1 inch were cut from the sheet and were compressionmoulded and cured for 45 minutes in the mould at a temperature of C. Thecutting resistance of the cured slab was measured and compared with aconventional golf ball cover compound. Cutting resistance is given inarbitrary figures, a higher figure indicating a better resistance. Theresults are given in Table l.

A ball (diameter 1.62 inches) was then moulded from the composition andcured, and its resistance to cutting in play and its flightcharacteristics were determined and were compared with a conventionalthread-wound range ball, as shown in Table l EXAMPLE II Twenty-seven andfive tenths parts by weight of a crystalline high density homopolymer ofethylene, melt flow index 0.9 g./10 min. (B.S. 2782 Method 105C) weremixed with 72.5 parts of cis-polybutadiene (as in Example I) in aninternal mixer at a temperature of 160 C. to C. until a homogeneousblend resulted. Forty-eight parts of lead carbonate, three parts oftitanium dioxide and one part of yellow pigment were added and mixingcontinued until a homogeneous blend again resulted. The mix was cooledto 120 C. and 3.25 parts of dicumyl peroxide were added. Balls and slabswere moulded as in Example I and cured as previously described. Theresults of measurements and tests on the slabs and balls are given inTable I.

EXAMPLE Ill The method of preparation used in this Example was the sameas in Example ll except that the thermoplastic polymer employed was ahigh density copolymer of ethylene and butene-l (less than 5 percent byweight) having a melt flow index of 1.2 g./l0 min. The results of testson balls and slabs are given in Table l.

EXAMPLE IV The composition of Example I was sheeted on a mill and ex- Acover composition was prepared as follows:

Forty-seven and five tenths parts of a copolymer of ethylene andmethacrylic acid, containing 7 percent of the acid in which 85 percentof the acid was present as the sodium salt, and having a melt flow indexat 190 C. of 0.5 g./l min. were mixed with 52.5 parts of thecis-polybutadiene described in Example 1, in an internal mixer at150-170 C. until a homogenous blend resulted. Forty-two parts of leadcarbonate, 3.75 parts of titanium dioxide and 0.25 parts of a pigmentwere added and the mixing continued until a homogeneous blend againresulted. The mix was cooled, chipped in a granulator and 3.5 parts ofdicumyl peroxide were added by tumble mixing. The blend was thencompression moulded into a rough sheet at 100l20 C. and rapidly cooledto room Resilience Coefficient of restitution determined by firing aprojectile at the ball and noting the time taken for ball and projectileto travel a predetermined distance. CH Compression Hardness Click is thesound made by contact between the golf club and the ball.

Carry" represents the distance travelled by the ball from where it isstruck to where it first lands on the ground.

Total distance" represents the distance travelled by the ball from whereit is struck to where it finally comes to rest on the ground andTrajectory is an arbitrary scale for comparing the heights to whichballs rise during flight, a higher figure indicating a higher flightpath.

The data are as follows:

TABLE I Total CR Re- Resil- Carry distance Trajec- C R (b) (s) H boundience OH Click (yds.) (yds.) tory A G00 335 72 70 0. 551 87 Fairly good-188 256 21% B Fairly good 325 61 71 0. 524 78 d 170 235 19% d 335 61 73O. 509 171 244 19% 340 70 66 0. 560 196 255 20% It will be seen from theabove that the play balls produced by the invention have similarproperties in some respects to conventional range balls and in somerespects are superior. 7

temperature. The resulting sheet had a nominal thickness of 0.125 inch.

Slabs 3 inches by 1 inch were cut from the sheet and were compressionmoulded to 0.120 inch thickness and cured for 45 minutes in the mould ata temperature of 160 C. The

cutting resistance of the cured slab was measured and compared with aconventional golf ball cover compound. Cutting resistance is given inarbitrary figures, a higher figure indicating a better resistance. Theresults are given in Table 1 below.

Golf ball hemispherical half-shells having an internal diameter of 1.0inch and wall thickness 0.310 inch were moulded from the above covercomposition by heating at l00-l10 C. in a mould and cooling prior toextraction. The cores already prepared were coated with a 20 percentsolution of triphenyl methane triisocyanate in methylene chloride andthe solvent allowed to evaporate. Two half-shells were placed around atreated core and moulded in a dimpled mould at 160 C. for 45 minutes,followed by cooling prior to extraction, to produce a golf ball (D) 1.62inches diameter of weight 45.1 grams. The golf ball was then comparedwith a conventional thread-wound range ball with regard to itsresistance to cutting in play and its flight characteristics. Theresults are given in Table 1.

EXAMPLE V The composition of EXAMPLE 11 was sheeted on a mill andextruded as a rod 1.125 inches diameter in a cold extruder. Sphericalcores 1.04 inches diameter were moulded from plugs of the extrudate for7 'rninutes at 150 C.

Slabs 3 inches by 1 inch and golf ball hemispherical cover half-shellswere prepared and a golf ball (1.62 inches diameter) weight 45.7 gramsmoulded around the above cores using the same method as used in Example1V.

For purposes of comparison a conventional thread-wound ball (F) ofdiameter 1.62 inches was subjected to the same series of tests as theballs and slabs made by following the procedures of Examples 1, II, 111,[V and V (A, B, C, D and E respectively).

In Table l the headings to the various columns have the followingmeaning:

CR (b) Cutting resistance of the ball. CR (s) Cutting resistance of aslab of the composition. H Hardness (Shore C 7 V W T156555?lercentrebound from a height of 100 inches onto a solid concrete base.

We claim:

1. A substantially spherical moulded solid golf ball of a compositionproviding the gravity, click, rebound and size required for a golf ballcomprising a polymer blend consisting essentially of rubber and athermoplastic substantially crystalline homopolymer of an alpha-monoolefin having from 1 to 6 carbon atoms or a copolymer of alpha-monoolefins having from 1 to 6 carbon atoms, the rubber being selected fromthe class consisting of polybutadiene, copolymers of butadiene withacrylonitrile, copolymers of butadiene with styrene, elastomericcopolymers of ethylene with an alpha-olefin higher than propylene, andpolyisoprene and said rubber being present in the blend in an amount offrom 50 percent to percent by weight of the blend.

2. A golf ball according to claim 1, which is a one-piece moulded ball.

3. A golf ball according to claim 1, which consists of a core encased ina cover, the core consisting essentially of the blend of claim 1.

4. A golf ball according to claim 3, in which the core consists of aspherical inner core surrounded by a spherical shell, at least one ofwhich consists essentially of the blend of claim 1.

5. A golf ball according to claim 4, in which the spherical inner coreis selected from the group consisting of a glass ball and a steel balland in which the spherical shell consists of at least two hollowsemisphen'cal shells consisting essentially of the blend of claim 1.

6. A golf ball according to claim 1, in which the rubber is present inan amount of from 60 percent to 80 percent by weight of the blend.

7. A golf ball according to claim 1, in which the rubber is apolybutadiene.

8. A golf ball according to claim 7, in which the rubber is a blend ofcis-polybutadiene with natural rubber and/or one or more syntheticrubbers.

9. A golf ball according to claim 8, in which the cis-polybutadiene ispresent in an amount of at least 50 percent of the bland.

10. A golf ball according to claim 1, in which the alphamono olefin isethylene.

11. A golf ball according to claim 1 wherein said blend is cured with anorganic peroxide or sulfur or by irradiation.

12. A golf ball according to claim 11 wherein said blend is cured withan organic peroxide at a temperature of from to 250 C.

13. A golf ball according to claim 12 wherein said organic peroxide isdicumyl peroxide.

14. A golf ball according to claim 1' wherein said crystallinehomopolymer is selected from the group consisting of polyethylene,isotactic polypropylene, isotactic polybutene-l andpoly-4-methyl-pentene-l and wherein said copolymer is a copolymer of thealpha-mono olefin of said crystalline homopolymer with a copolymerizablealpha-mono olefin selected from the group consisting of butene-l,hexene-l, ethylene and propylene provided that said copolymerizablealpha-mono olefin and said alpha-mono olefin of said crystallinehomopolymer are different.

15. A golf ball according to claim 14 wherein said copolymer is aterpolymer of said copolymerizable alphamono olefin, said alpha-monoolefin of said crystalline

1. A substantially spherical moulded solid golf ball of a compositionproviding the gravity, click, rebound and size required for a golf ballcomprising a polymer blend consisting essentially of rubber and athermoplastic substantially crystalline homopolymer of an alpha-monoolefin having from 1 to 6 carbon atoms or a copolymer of alpha-monoolefins having from 1 to 6 carbon atoms, the rubber being selected fromthe class consisting of polybutadiene, copolymers of butadiene withacrylonitrile, copolymers of butadiene with styrene, elastomericcopolymers of ethylene with an alpha-olefin higher than propylene, andpolyisoprene and said rubber being present in the blend in an amount offrom 50 percent to 90 percent by weight of the blend.
 2. A golf ballaccording to claim 1, which is a one-piece moulded ball.
 3. A golf ballaccording to claim 1, which consists of a core encased in a cover, thecore consisting essentially of the blend of claim
 1. 4. A golf ballaccording to claim 3, in which the core consists of a spherical innercore surrounded by a spherical shell, at least one of which consistsessentially of the blend of claim
 1. 5. A golf ball according to claim4, in which the spherical inner core is selected from the groupconsisting of a glass ball and a steel ball and in which the sphericalshell consists of at least two hollow semispherical shells consistingessentially of the blend of claim
 1. 6. A golf ball according to claim1, in which the rubber is present in an amount of from 60 percent to 80percent by weight of the blend.
 7. A golf ball according to claim 1, inwhich the rubber is a polybutadiene.
 8. A golf ball according to claim7, in which the rubber is a blend of cis-polybutadiene with naturalrubber and/or one or more synthetic rubbers.
 9. A golf ball according toclaim 8, in which the cis-polybutadiene is present in an amount of atleast 50 percent of the bland.
 10. A golf ball according to claim 1, inwhich the alpha-mono olefin is ethylene.
 11. A golf ball according toclaim 1 wherein said blend is cured with an organic peroxide or sulfuror by irradiation.
 12. A golf ball according to claim 11 wherein saidblend is cured with an organic peroxide at a temperature of from 150* to250* C.
 13. A golf ball according to claim 12 wherein said organicperoxide is dicumyl peroxide.
 14. A golf ball according to claim 1wherein said crystalline homopolymer is selected from the groupconsisting of polyethylene, isoTactic polypropylene, isotacticpolybutene-1 and poly-4-methyl-pentene-1 and wherein said copolymer is acopolymer of the alpha-mono olefin of said crystalline homopolymer witha copolymerizable alpha-mono olefin selected from the group consistingof butene-1, hexene-1, ethylene and propylene provided that saidcopolymerizable alpha-mono olefin and said alpha-mono olefin of saidcrystalline homopolymer are different.
 15. A golf ball according toclaim 14 wherein said copolymer is a terpolymer of said copolymerizablealpha-mono olefin, said alpha-mono olefin of said crystallinehomopolymer and butadiene wherein said butadiene is present in an amountless than 10 percent of the other monomers.
 16. A substantiallyspherical moulded solid golf ball having the gravity, click, rebound andsize required for a golf ball comprising a blend of polybutadiene and athermoplastic substantially crystalline homopolymer of ethylene or acopolymer of a major amount of ethylene and a minor amount of anotheralpha-mono olefin having from 1 to 8 carbon atoms, said polybutadienebeing present in an amount of from 50 percent to 90 percent by weight ofsaid blend.